textproduct: Albany

WHAT HAS CHANGED

Expanded the Winter Weather Advisory for today into tonight to include Berkshire County and western Rensselaer County where 2 to 5 inches of snow is expected in addition to a glaze of ice from patchy freezing drizzle.

Storm total snowfall amounts have increased slightly for the southern Adirondacks and the southern Greens mainly due to upslope snow expected after Midnight tonight. There is now a 25 to 40% chance that 24-hour storm total snow amounts exceed 6 inches; however, coverage is not high enough to warrant an upgrade to a winter storm warning.

West-northwest wind gusts after Midnight tonight into early Wednesday morning turn strong with a 30 to 70% chance of exceeding 40mph in the eastern Catskills, parts of the Capital District, the Rensselaer Plateau, and western MA. Given that the greatest potential of exceeding 46mph is limited to a short duration (09 - 15 UTC Wed), did not issue a wind advisory. Will continue to monitor.

The timing of our next winter weather event late this week has trended later now arriving Friday evening and continuing into Saturday. Colder temperatures now favor mainly snow as the p-type, increasing confidence for slippery travel conditions. The highest probabilities for 7"+ of snow has trended near and south of I-90 as the storm track remains focus in the mid- Atlantic.

KEY MESSAGES

1. Slippery travel today into this evening from an initial period of mainly light snow that weakens and transition to patchy freezing drizzle this evening. Upslope snow showers and gusty winds after Midnight tonight in higher terrain areas will likely lead to reduced visibility.

2. After a relatively quiet stretch Christmas Eve/Day, there is increasing confidence for slippery travel conditions Friday night into Saturday from another period of snow. There is a 25 to 45% chance for snowfall amounts to exceed 7 inches focused mainly near and south of I-90.

3. Additional slippery travel conditions are possible Sunday as cold temperature ahead of our next storm system favor a period of wintry mix including potential freezing rain before changing to plain rain.

DISCUSSION

KEY MESSAGE 1...

Latest water vapor imagery early this morning shows our compact shortwave tracking through Manitoba/western Ontario with strengthening mid-level isentropic lift ahead of its warm front resulting in an expanding region of light snow overspreading western NY/PA. As mid-level FGEN and warm air/moisture advection continues increasing this morning, snow will spread north and eastward initially reaching the eastern Catskills, mid Hudson Valley, NW CT and western Mohawk Valley by daybreak before expanding north/east into the Capital Region, SW Adirondacks and eventually into western MA and southern VT between roughly 7 and 10 AM. Snowfall intensity remains mainly light this morning as overall forcing for ascent remains weak with forecast soundings only showing a few hours this morning where forcing intersects the DGZ leading to snowfall rates from a few tenths up to 0.5" or snow mainly from 12 - 18 UTC. The HREF highlights the Catskills in Ulster County as areas where snowfall rates can reach 0.50 - 0.75" per hour at times this morning mainly due to upslope enhancements. While snow begins during the A.M commute today (especially for areas south of I-90), even light coatings of snow can lead to slippery travel given temperatures in the 20s to low 30s.

Periods of light snow weaken from SW to NE this afternoon mainly for areas near and south of I-90 as southwest flow downslopes off the Catskills and our mid-level dry slot advances northeastward. As snow tapers off and the mid-levels dry out, patchy freezing drizzle will need to be monitor this afternoon into this evening where sfc temperatures remain near or under freezing mainly across the southern Adirondacks, Mohawk Valley, Taconics, Lake George region, western New England, and the northern/eastern Catskills as clouds tops warm and no longer support ice nuclei. Valley areas should warm into the mid-30s, reducing the potential for freezing drizzle.

Total snowfall amounts through 7 PM today should generally range from 1-3 inches, with the greatest amounts in the eastern Catskills, SW Adirondacks, southern VT and northern Taconics where amounts can reach 3-5". After midnight tonight, our intensifying and rather vigorous shortwave will track overhead sweeping an arctic cold front through the region. A surge of cold air advection and a strengthening pressure gradient in its wake will result in a period of upslope snow showers across the southwest Adirondacks into the southern Greens, northern/eastern Catskills, the northern/central Taconics and western MA with an additional 1 to 3 inches expected. The highest amounts are likely on the west facing slopes of the southern Greens and southern Adirondacks. Forecast soundings show west-northwest winds turning quite gusty by 06 - 09 UTC due to the strong cold air advection regime with a 50 to 70% chance for wind gusts to exceed 30mph, mainly focused down the Mohawk Valley, eastern Catskills, southern Adirondacks, Capital District into western MA. Combination of falling snow and gusty winds will likely reduce visibility and lead to difficult travel in higher terrain areas. Upslope snow showers end early Wednesday morning with gusty winds diminishing by 15 - 18 UTC.

KEY MESSAGE 2...

A 1035hPa high builds into Quebec for Friday with northerly winds funneling a cold air mass into the Northeast. The colder trend seen over the last few model cycles continue with the latest probabilistic guidance from the NBM showing a 60 to 80% chance regionwide for daytime temperatures on Friday to fall under 25 degrees. The consensus among the latest deterministic and ensemble continues to grow in our next winter weather event arriving Friday P.M/evening as a shortwave embedded in the conveyor belt of fast west-northwest flow aloft tracks from the Great Lakes into the mid-Atlantic. As the thermal/moisture gradient tightens and enhances baroclinicity, a sfc low develops resulting an area of precipitation overspreading the mid- Atlantic into the Northeast. The track of the sfc low continues to be favored well to our south in the mid-Atlantic as the Canadian high and cold air mass remains locked to our north. As a result, the precipitation type continues to favor mainly snow Friday night into Saturday with probabilities for 24-hr precipitation amounts of at least 0.50" highest in the eastern Catskill, mid-Hudson Valley, Litchfield Hills and areas mainly south of I-90 ranging 40-60%. This can result in moderate snow accumulations and potential slow downs for any holiday travel. Snow amounts look to decrease heading north of I-90 as precipitation amounts trend lower.

KEY MESSAGE 3...

Our active weather patterns continues with yet another storm system to watch for the end of the weekend on Sunday. With the Canadian high positioned to our north and the storm tracking to our west, confidence in a wintry mix is increasing including potential for sleet and freezing rain as shallow cold air is overrun by warm air aloft. Latest probabilities guidance from the NBM shows widespread 40-60% chance values for at least a hundredth of an inch of ice from freezing rain from 7am to 7pm Sunday. Given this event is still 5 days away, our latest forecast shows rain/snow mix in collaboration with neighboring WFOs but note that the anticipated weather pattern is a classic signature for freezing rain and should it continue, we likely will show more wintry mix and ice accumulations in future updates. Again, this can result in hazardous travel conditions for those returning from the holiday weekend on Sunday.

AVIATION /06Z TUESDAY THROUGH SATURDAY/

Through 06z Wednesday...VFR conditions will prevail through around 11z or 12z. Then widespread light snow will develop with initially MVFR conditions for an hour or two followed by prevailing IFR conditions in the -SN at all TAF sites. The -SN and associated IFR should last through the day, with steady snow becoming lighter and spotty by early evening. IFR cigs will likely linger though despite improvements in VSBY to MVFR. Will add mention of PROB30 for -FZDZ at KPSF as ice nuclei is lost between 01z-06z Wednesday. Winds will initially be near clam, becoming southerly around 4-7 kt after 12z.

Outlook...

Wednesday Night: No Operational Impact. NO SIG WX. Christmas Day: Low Operational Impact. Breezy. NO SIG WX. Thursday Night: Low Operational Impact. Breezy. NO SIG WX. Friday: Moderate Operational Impact. Chance of SN. Friday Night: High Operational Impact. Likely SN. Saturday: Moderate Operational Impact. Chance of SN. Saturday Night: Moderate Operational Impact. Chance of SN. Sunday: High Operational Impact. Definite RA...SN.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...Winter Weather Advisory from 7 AM this morning to 7 AM EST Wednesday for NYZ032-033-038-039-054-082. Winter Weather Advisory until 5 PM EST this afternoon for NYZ063. MA...Winter Weather Advisory from 7 AM this morning to 7 AM EST Wednesday for MAZ001-025. VT...Winter Weather Advisory from 7 AM this morning to 7 AM EST Wednesday for VTZ013-014.